The preparation of aluminum-reduced titanium trichloride catalysts is well known, and such catalysts are widely employed in the production of polyolefins, such as polyethylene and polypropylene. The preparation of such catalysts and their use in polymerization reactions is discussed in a number of patents, for example, in U.S. Pat. Nos. 3,121,063, 3,475,394, 4,154,702, 3,642,746 and 3,647,772, and in British Pat. No. 1,310,547.
It is also known that the performance of such catalysts can be improved by treatment with electron donor substances. Details of such treatment and examples of electron donors which have been employed are disclosed in, among others, U.S. Pat. Nos. 3,186,977, 4,110,248, 4,111,836, 4,115,319, 4,126,576, 4,127,504, 4,127,505, 4,142,991, and British Pat. No. 1,310,547.
However, the treatment of aluminum-reduced titanium trichloride catalysts with electron donors containing an OR radical, illustratively with various ethers, may result in the generation of by-products which adversely affect the catalysts. For example, they can generate undesirable pressures in the shipping container. In other instances the by-products which are formed may be toxic. This introduces an element of hazard which it is clearly desirable to avoid.